1. Field of the Invention
The present invention relates to an apparatus for controlling an electronic throttle valve in which a throttle valve provided in a suction path of an engine is driven to be opened and closed by a motor, and more particularly, to an electronic throttle control suitable for throttle opening control at a small opening.
2. Description of the Related Art
There have recently been active movements toward realization of constant-speed cruise control, traction control and lean-burn control based on electronic control of a throttle valve. While specially-designed idle speed control (ISC) valves have heretofore been used for ISC control because of the need for performing throttle valve control for positioning with high accuracy, a method of performing ISC control using an electronically-controlled throttle has been conceived as a method enabling ISC control without using a specially-designed ISC valve. However, there is a need for accurate control at a small throttle valve opening since the air flow rate during idling is low.
Ordinarily, a throttle valve opening sensor for obtaining information on the throttle valve opening is used to indicate information from the completely closed state to the fully opened state through the output in a range from 0 to 5 V. For this reason, means for changing the accuracy of an A/D converter used in combination with a microcomputer or changing the characteristics of a throttle valve opening sensor and a throttle valve opening sensor input circuit have been devised to improve the control resolution of the throttle valve opening.
For example, in the art disclosed in JP 5-263703 A, two A/D converters are used to detect the throttle valve opening. The output from a throttle valve opening sensor is directly input to one of the two A/D converters, while the output from the throttle valve opening sensor is amplified before being input to the A/D converter. When higher accuracy is required in low-opening control such as ISC control, the amplified input from the throttle valve opening sensor is employed. The direct input is employed when the opening is large, that is, when the necessary accuracy is not so high. ISC control is thus realized.
To improve the control accuracy of the throttle valve opening, a system such as that described above is required which has a throttle valve opening sensor input circuit, two A/D converters, and a signal amplifier, and there is therefore a problem of increase in costs for manufacturing a control apparatus having such components.
In view of the above-described circumstances, an object of the present invention is therefore to provide an electronic throttle valve control apparatus which has a high throttle valve opening resolution, and which can be manufactured at a low cost.
In order to achieve the above-mentioned object, according to the present invention, there is provided an apparatus for controlling an electronic throttle valve in which a throttle valve provided in a suction path of an engine is driven to be opened and closed by a motor, said apparatus including: a target throttle opening computation unit for computing a target throttle opening of the throttle valve; an actual throttle opening detector for detecting an actual opening of the throttle valve; a control-use actual throttle opening computation unit for computing a control-use actual throttle opening by adding a predetermined number of times the actual throttle opening detected value obtained by said actual throttle opening detector; and a throttle valve controller for controlling the throttle valve on the basis of an opening deviation between the target throttle opening and the control-use actual throttle opening.